The objectives of this study involve the evaluation and ranking of various existing and new dental restorative materials with regard to in-vivo wear resistance and abrasion. The wear characteristics of various materials, and their potential to wear other materials and to abrade the natural teeth they oppose, has been a major concern to the dental profession. The significance of this research area is directly related to the quality of the dental care provided patients, and the establishment of a new and seemingly valid, and reliable in-vivo testing system for examining the efficacy of intraoral use of some of the currently available materials and some new materials recently formulated. In a broad concept, this proposal involves: 1.) the further development of the accuracy of a three-dimensional digitizing and computer-graphics measuring system to determine in-vivo, the longitudinal wear and abrasion of various dental restorative materials; 2.) to evaluate and rank in-vivo, the abrasion resistance of restorative dental materials, commercially available and experimental; and 3.) to specifically, determine in-vivo, the abrasion resistance of different types of composites, and different types of high copper amalgam alloys (unicomposition and ad-mixed), as well as different groups of cast-metal restorations.